Schiit Folkvangr Review - Measures like shit, but sounds GRRREAT

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by purr1n, Jun 30, 2022.

  1. purr1n

    purr1n Burned out

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    Part of it is because this is a one of a kind with no transformers, no coupling caps. Well, there was the Futterman OTL from Cavalli which I assume only had interstage coupling caps. We just don't have much to compare the Folkvangr to because so much contributes to the sound. The white-cathode follower has a sound. The type tubes have a sound. The high plate resistance of the tubes will have an effect which will result in sound.

    What is mistakable is that the Folkvangr has a sound which I think @roshambo123 and I have tried to describe.

    Valhalla 2 is a good place to start. Folkvangr is a Valhalla 2 with moar output devices and without the coupling caps. While we can argue that perhaps Valhalla 2 can be improved with audiophile boutique coupling caps, with maybe the big oil cans used on the EC ZDS - this would not only break the price point but also the form factor.

    Basically add balls and drive to Valhalla 2, remove the veil, and smooth out the highs, while keeping the soul of the Valhalla 2, and voila Folkvangr. I would say that the results, very positive effects, were unexpected.
     
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    Last edited: Jul 6, 2022
  2. roshambo123

    roshambo123 Friend

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    If we'd like to dig into this a little, I'll bring up a review that Amir did of another OTL (although not OCL), the Darkvoice 336SE.

    So, the DarkVoice's SINAD is about a match for Folkvangr's, although you can clearly see from his 1khz tone that there's a boatload more harmonics on 336SE. I also have both amps and they are not close on technicals, Folkvangr is tiers above the $200 chinese amp.

    Still, Amir concludes "People though get such products for their subjective qualities. There, I can confirm the appeal of using the 336SE with high impedance headphones of 300 ohm and higher. There is copious amount of power here, and what distortion there is, is masked for the most part. In my experience of either power amplifiers or headphone, how much power you have available determines fidelity first and foremost. Lack of power results in anemic sound which seems to lack impact, and even resolution. The high output voltage of DarkVoice 336SE gives it such a strong advantage that it can override its much higher distortion. With that distortion following perceptual masking, it is not as much of a detriment as it may seem at first."

    So power is what makes tubes good? Hmm. 336SE is rated as 1W (not sure on load, but I'll bet 300 ohm) and Folkvangr is 1.2W into 300 ohms. Seems like kinda similar power. Perhaps it is something else? Because the performance delta between these amps is huge. Clearly, if SINAD fails us here, we can't just promote power as the new OneGod™ and conclude based on that rating if something is good. There are clearly other factors at play.
     
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  3. Armaegis

    Armaegis Friend

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    I'm just waiting for someone to try and snag two of these and butcher it with adapter cables into some unholy monoblock config. Yeah we know it wasn't recommended, but I bet someone will try.
     
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  4. purr1n

    purr1n Burned out

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    Don't know what he is saying about copious amount of power. Darkvoice is not a powerful amp. Let's pick a standard for "calculating" power out of "thin air". Usually it's spec'd at 1%, but let's use a slightly more stringent standard and take the power rating when we reach 0.50% THD which is -46db. ASR looks at THD+N instead of THD, but at higher levels, there will be less N. The DV 336E will have 2.5mW of power into 300-ohms.

    upload_2022-7-7_7-51-41.png
    DV 336E has 2.5mW of power into 300-ohms at about 0.50% THD+N (N probably doesn't play much of part, but good enough for next comparison.

    Next let's look at Folkvangr. Let's take -49db THD at 0.775 Vrms and extrapolate from that. Let's say by 0.825Vrms the THD reaches 0.50% THD. We should be more or less there. Rough estimate to determine "high power" is what we are looking for.

    P=V^2 / R
    (0.850)^2 / 300 = 0.0024

    upload_2022-7-7_7-55-4.png
    Let's extrapolate and assume 0.850Vrms the THD reaches 0.50% (-46db) THD. From calcs, Folkvangr has roughly 2.4mW of power into 300-ohms at about 0.50% THD.

    For comparison, Magni 3+ probably does well over 300mW into 300-ohms.

    Power summary, apples to apples, power into 300-ohm loads at 0.50% (-46db) THD some estimated / rough-ballpark:
    • Folkvangr 2.4mW
    • DW 336SE 2.4mW
    • Magni 3+ 300.0mW (+)
    I'll let you make the decision of what constitutes "high power". Science relies on math, not on what people say. The strange this about this hobby is that there are dudes with expensive measurement who just blurt out random stuff, words, relating to measurements, which are not supported by the measurements. We've even seen this from "established" big guns from time to time at the ORFAS audio rags.

    @Woland: We discussed previously of the sonic changes to taking out the coupling cap from the Valhalla 2. Let's discuss tube types. Now the WCF circuit of the Valhalla and Folkvangr can be said to have thick or fuzzy lows, a warm rich or even thick and bloomy sound. It this a characteristic of the WCF or is this a characteristic of the tubes highish plate resistance. Now what would happen if the 6AS7 with its super low plate resistance were used?

    Also, neither this amp or the Valhalla I find particularly "wet". IME, I found the "wet" sound often to a function of the combination of specific tubes, transformers, coupling cap, bias. Certain transformers will have a wetter sound. Sometimes it's specific power tubes from China. I don't think I've ever heard small tubes that sounded wet.
     
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    Last edited: Jul 7, 2022
  5. Beefy

    Beefy Almost "Made"

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    I mean, all these possibilities sound great to me! But if there is no appetite for this, I wonder whether we'll ever see Schiit's take on a DHT SET amp.

    We have bespoke DHT SETs from people like Eddie Current and Donald North that people love. But I bet Schiit could do an amazing job of something more accessible. Just by switching to S/S rectifiers and building on a PCB seems like it could create a pretty decent economy-of-scale for a one-box mass-market amp.
     
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  6. lagadu

    lagadu Facebook Friend

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    SS rectifier sure, but DHTs seem to all be low volume/silly expensive nowadays, not sure it would be a good match for a high volume product.
     
  7. Beefy

    Beefy Almost "Made"

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    Sure, but I've always assumed a big part of that is the labor of a P2P wired amp. Are there any 300B headphone amps based on a PCB? We know it can be done because of the Elekit DIY amps...
     
  8. roshambo123

    roshambo123 Friend

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    Not a business person, but I'd hazard a guess the business prospects of a DHT SET aren't stellar.

    I believe there is a lot of fixed cost built into DHT SET's due to the carefully paired tubes, caps, and transformers.

    You might be able to undercut a little by using assembly line techniques and PCB's, but you'll still be up against similar design offerings from ampsandsound and Woo, and your product is still going to be relatively expensive just from the parts.

    High price reduces volume and therefore negates the assembly line benefit, so you're probably not undercutting as much as you'd want.

    That's my naïve guess anyway.
     
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  9. Beefy

    Beefy Almost "Made"

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    It's probably not a bad guess. It might be impossible. But if anyone can make it happen, I'd put my money on Schiit.
     
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  10. will_f

    will_f Friend

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    I think for a lot of people, part of the appeal is the hand made, bespoke nature. I have to admit, it’s part of the appeal to me.
     
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  11. Wilewarer

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    Who knows, maybe we see something more interesting than their take on a DHT. For business stuff, I suspect the most relevant question was actually "how well is a 2000 dollar headphones-only amp from us going to sell?", and depending on the answer maybe in who-knows-how-many years there's some other sufficiently interesting/unique thing that turns out to be good-sounding enough to justify being built to that price point.

    I mean, Yggdrasil is already a big expensive thing that sells well from them, but this is narrower use still.
     
  12. atomicbob

    atomicbob dScope Yoda

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    Agree with most of this post but take exception to "poor measurements".
    Poor measurements only if we use the outdated 1940s interpretation of THD+N (or SINAD) as having any correlation to audio component sound quality.

    From @purr1n 's -20 dBu measurement a more modern interpretation.
    First, why -20 dBu? At that level many modern headphones have sensitivities consistent with approximately 80 dBSPL, a more reasonable listening level than 100 dBSPL at 0 dBu. For more information search "the magic of 83 dB SPL".

    20220701 Folkvangr 1KHz distortion spectrum -20 dBu annotated.png
    THD+N is dominated by D2 (2nd harmonic distortion) in this measurement which is 0.56%. Yet D2 is not directly audible to most people until somewhere between 1% and 10%. Some might find D2 adds a low level richness to recreational listening.

    D3 on this graph is far down at 0.0025% and 4+HD+N, excluding AC mains noise is a scant 0.003%.
    60 Hz is 0.2% but with an absolute of -75 dBu will be inaudible in most ordinary listening spaces with most headphones, especially when considering the ISO contours of equal loudness for the Human Auditory System (HAS). 120 Hz is down another 10 dB and likely inaudible.

    I am assuming Folkvangr has a low NFB. Low NFB combined with low 4+HD+N and AC mains below -75 dBu are indicative of a headphone amp that will provide perceived good sound.

    It would be very useful to see this same measurement at -30 and -40 dBu. AC mains noise will remain constant. 4+HD+N may continue to drop.
     
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  13. purr1n

    purr1n Burned out

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    It's only at the peaks, 90-100db, where overall THD rises, with the appearance of 3rd, 4th, 5th harmonics in a nice way (descending pattern). This is what I mean by "vintagey", reminds me of the tape decks, how that old gear would sound as the levels hit saturation, the yellow or red LEDs. I'm pretty sure if we got a rise in odd order harmonics, or even small level of higher order harmonics, my head would have exploded.

    upload_2022-7-7_17-16-6.png

    I'll see if I can grab it again for moar measurements.
     
  14. kukur9

    kukur9 Acquaintance

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    Any sense in trying the Folkvangr as a preamp to SS amp and speakers?
     
  15. will_f

    will_f Friend

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    If that’s all you’re going to do and you don’t intend to use the headphone amp part, there’s cheaper ways to live the dream. Schiit makes some decent tube preamps that will save you the price of a nice speaker amp.
     
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  16. scblock

    scblock Friend

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    On the other hand if you already have it in house, it wouldn’t hurt to try it and see what it’s like.
     
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  17. kukur9

    kukur9 Acquaintance

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    I was sort of toying with the idea, and hoping someone here would try it!

    Yes, there are cheaper and my Saga+ does its job fine for what it is. It is not anything near the AI Modulus 2A, however, but that is unfair apples and oranges.
     
  18. roshambo123

    roshambo123 Friend

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    Probably not quite the test you were looking for but I used it as a preamp for my Bose Companion 20 desktop speakers. The preamp outs work. Unlike MJ2, you have to pull the headphone connection to get the preamp outs to fire up. I wasn't hearing anything special. Honestly, I prefer MJ2's preamp outs since they make the tiny Bose speakers sound wider and bassier than they are. I feel like Folkvangr's pre outputs are basically utilitarian, although my example is a shitty test.
     
  19. Elmer Danilovich

    Elmer Danilovich MShenay trying to pretend to be an old man

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    Literally kicking my self for this reason as well... like this is the worse time for me to be buying an amp but fuck as much as I enjoyed Vali 1 this seems like the eventual upgrade I always wanted and so I kinda wanna get one in black asap
     
  20. stretchneck

    stretchneck Rando

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    Folkvangr measures pretty well actually, just a shame that 50Hz isn't tamed a little better.
     

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